The grass is already starting to regrow. Warm nights and nightly rains, plus lengthening daylight is triggering growth faster than I expected. Green is already covering over the tannish thatch residue.
Most of the regrowth is 1/4"-1/2", but some is over a full inch! And it's nice and green.
About 2/3 of the area has now been sprayed with 20% acetic acid (vinegar). I find that I can get foliage burn/kill as long as the foliage is very young, tender, and rapidly growing. If I add dormant oil or clove oil, the results are even better. And if I can apply it on a brilliant sunny day it works even better. Getting those perfect sunny days are difficult right now, but I happened to have hit one (by accident I'm sure). I had enough vinegar/clove oil to do those areas with the very short, lush regrowth.
I fully expect to see good foliage kill. But I won't get root kill with this method on established grass. But it should zap any grass seedlings. But if I run the rototiller over just the surface (remember the rocks? Can't dig the tiller in deeper than 1/2"-3/4"), I should be able to cut a lot of the plants just below the surface, thus killing a good percentage. Then if I respray followed by re-tilling as I see regrowth, I should in theory get the grass controlled and hopefully mostly killed. We shall see if this experiment works.
1/3 of the garden area has grass too long for using this method. The sheep and horse did not graze that area down as closely. I currently have chickens and rabbits mob grazing it down. They have about 1/2 of the area completed. As the grass regrows I plan to treat it the same way, trying to eliminate it. Currently I'm out of 20% vinegar but I'm in the process of making more. So I should be ready to spray again tomorrow if the weather is right.
Mob grazing with rabbits and chickens involves using 2'x4' wire cages with no bottoms. With the rabbits I put four young littermates per cage. The cage is moved as soon as they graze the grass down, which is proving to be 6 times a day. With the chickens I put 6 chickens per cage and put the chickens into the cage at dawn, leaving them there until noon. They are then released to forage and eat their normal chicken food. They are hungriest first thing in the morning so greedily eat the grass.
This overall method, using the vinegar/clove oil + mob grazing + rototillering will be more expensive and considerably more time consuming that spraying one treatment of Round-up. But I'm willing to do it and it will be a nice experiment to determine how well it works.